Mixing and conveying means



Sept. 30, 1969 c, FUTTY ETAL 3,469,824

MIXING AND CONVEYING MEANS Filed Feb. 27, 1968 CEMENT M-WM'EQ 5 2 SAND Gum/Rm mscommuous CNZBHDE STRUCTUQE CON NUOUS CARBlDE- United States Patent 3,46,824 MIXING AND CONVEYING MEANS Robert C. Futty, Willow Street, and John L. Kugle, Lancaster, Pa., assignors to IRL Daflin Associates, Incorporated, Lancaster, Pa., a corporation of Pennsylvania Filed Feb. 27, 1968, Ser. No. 708,679 Int. Cl. B28c /14; B01f 7/08, 7/04 US. Cl. 259-178 5 Claims ABSTRACT OF THE DISCLOSURE .This invention relates to mixing devices, and more particularly to an improved concrete mixing and delivery system.

Numerous forms of mixing troughs and associated conveying means have been known and used for a considerable length of time. The majority of such devices have been formed of an elongated chute having a relatively conventional mixing paddle or mixing screw disposed therein. Such prior art systems have suffered from several disadvantages. The first of these has been an inability to withstand the abrasive effect of materials being mixed within the trough, especially when the materials are of a highly abrasive nature, such as concrete. A second such disadvantage in the prior art devices has been that the mixing troughs do not provide a mixing action which fully and completely mixes a liquid and a plurality of varied dry ingredients to obtain a substantially homogeneous composition therefrom. Additionally, the prior art devices are usually designed to perform only a simple mixing operation, and are not adapted to mix a plurality of constituents and to positively feed such constituents outwardly from the mixing trough.

Certain of the disadvantages in the prior art devices were recognized and overcome by the invention defined in Patent No. 3,310,293, for Concrete Mixing and Delivery System, issued Mar. 21, 1967, in the name of Harold M. Zimmerman. In that patent there is defined and described a system wherein dry concrete constituents or ingredients are stored in separate storage compartments, and are selectively fed in predetermined proportions to a mixing trough wherein they are mixed with water to form concrete of desired properties. It was found that in a system of this type, wherein the dry constituents are of a particularly abrasive nature, there is a tendency for such dry constituents to create an abrasive action on the walls of the mixing trough. It was also found that it was necessary to fully and completely mix the water and the dry ingredients relatively rapidly, in

order to obtain fully mixed concrete in a relatively short length mixing trough.

A method and mixing trough construction is later defined and disclosed in Patent No. 3,339,898 for Mixing Method and Mixing Trough Construction, issued Sept. 5, 1967, in the names of Robert C. Futty and Harold M. Zimmerman, which eliminated these problems. In this latter patent a mixing trough having substantially rigid sidewalls and a flexible and resilient bottom wall which is yieldable during a mixing operation and which is resistant to abrasion from the materials being mixed is described. Disposed within the mixing trough is a combination mixing, agitating and conveying means formed by an elongated shaft having a plurality of specially disposed mixing blades and helical feeding screws disposed thereon. In operation, a plurality of dry particulate ingredients, such as sand, gravel, cement or the like, are introduced into the inlet end of the mixing trough and a liquid, such as water or the like, is likewise introduced at the same location, to be combined with the dry materials to form a somewhat fluent, viscous composition within the mixing trough. As the shaft rotates within the mixing trough, the mixing blades stir and lift the ingredients and combine the same while still directing the same forwardly toward the helical screw portion. The helical screw portion also serves tomix and combine the ingredients, and likewise functions to positively feed such ingredients toward the discharge end of the mixing trough and outwardly therefrom. During all of this mixing and conveying operation, the flexible bottom wall of the trough can yield somewhat, to thus create a form of kneading on the ingredients to aid in their combination and to thus enhance the properties of the homogeneous mixture formed within the trough.

It has now been found that the abrasive action of the material being mixed, such as concrete, creates a certain amount of wear on the specially disposed mixing blades and helical feeding screws. Eventually, this abrasive action impairs the etficiency of the combination mixing, agitating and conveying means thereby necessitating periodic inspection and replacement. Further, the wear is not always of an even nature so that a particular section of the combination mixing, agitating and conveying meas may wear before another section whereby the complete assembly must be replaced.

It is, therefore, a primary object of this invention to provide an improved mixing trough free of the foregoing and other such disadventages. In this same regard it is a basic object of this invention to provide an improved mixing trough which includes a combination mixing, agitating and conveying means which is resistant to the abrasive action of the material being mixed and further, to provide an improved mixing trough including a combination mixing, agitating and conveying means certain parts of which are easily replaced without the need for replacing the entire assembly.

Consistent with the foregoing, it is a specific object of this invention to provide a combination mixing, agitating and conveying means formed by an elogated shaft having a plurality of specially disposed mixing paddles and helical feeding screws disposed thereon, wherein said mixing paddles and feeding screws are of such construction that any worn parts thereof may be selectively removed and replaced whenever the need should arise and furthermore, to provide such mixing paddles and helical feeding screws which are constructed of a material, specifically a nickelcontaining cast iron alloy, having a unique resistance to the abrasive effects of the material being mixed, e.g., concrete.

Other objects, advantages and salient features of this invention will become apparent from the following detailed description which, taken in connection with the annexed drawings, discloses the preferred embodiment thereof.

In the drawings:

FIGURE 1 is a perspective view of one embodiment of a mixing trough incorporating the basic principles of this invention;

FIGURE 2 is a longitudinal sectional view through the mixing trough shown in FIGURE 1;

FIGURE 3 is a transverse cross-sectional view taken substantially on lines 33 of FIGURE 1;

FIGURE 4 is an enlarged perspective view of the mixing, agitating, and conveying means of the mixing trough shown in FIGURE 1;

FIGURE 5 is a front elevational view of one type of wear plate in accordance with the present invention;

FIGURE 6 is a front elevational view of another type of wear plate in accordance with the present invention;

FIGURE 7 is a front elevational view of still another type of wear plate in accordance with the present invention;

FIGURE 8 is a front elevational view of yet another type of wear plate in accordance with the present invention; and

FIGURE 9 is a curve demonstrating the siliconchromium relationship in a preferred material of construction of the wear plates of FIGURES 5-8.

As will be seen generally from FIGURES 1-3, the novel structure of this invention includes a mixing trough generally designated 10 embodying an elongated chute generally designated 12, a mixing and conveying means generally designated 14 disposed within the chute, and a means generally designated 16 for operating the mixing and conveying means 14.

The chute 12 includes a pair of spaced apart longitudinally extending substantially rigid sidewalls 18 and forward and rearward end walls 20 and 22, respectively, extending between the sidewalls 18. Forward and rearward end walls 20 and 22 are connected to sidewalls 18 as by welding or the like. The end portion of the chute adjacent the end wall 22 is utilized as the inlet end of the mixing trough 10, and the end portion of the chute adjacent end wall 20 serves as the discharge end of the same. Accordingly, sidewalls 18 can extend angularly upward as designated 24 and end wall 22 can extend angularly inward as at 26, thus forming a hood-like portion which serves to assure that the ingredients introduced into the trough will not spill outwardly over the side or end walls thereof, but will remain therein.

A continuous elastomeric sheet 28 forms the bottom wall of the chute 12. The term elastomeric as used herein denotes a material having rubber-like properties of flexibility and resiliency, and desirably a high degree of abrasion resistance. The elastomeric material may comprise natural or synthetic rubbers, synthetic resinous plastic materials, and other such similar materials although it should be understood that it is not limited thereto. The elastomeric sheet 28 is connected to the sidewalls 18 of the chute 12 in any suitable manner. As disclosed in the aforementioned U.S. Patent No. 3,339,- 898, and shown in FIGURES 1-3 hereof, one method of connection comprises a pair of metal strips 30 extending longitudinally of the sidewalls 18 with each such strip having either an integral or interconnected depending flange 32. The side edges of the elastomeric sheet 28 are clamped between the sidewalls 18 and the depending flanges 32. Additionally, securing means such as nuts and bolts or the like, may be used to insure that the sheet 28 is properly held in place. End wall 20 terminates a short distance above the elastomeric sheet 28 to form an outlet or dispensing opening 34 for the mixed composition.

The improved mixing and conveying means 14 includes an elongated linear shaft 36 disposed within the chute between its sidewalls 18 and above its bottom wall 28, with the opposite ends of the shaft 36 projecting through the end walls 20 and 22 by means of suitable journal bearings 38 in each of said walls.

Along the shaft 36 are disposed a plurality of mixing elements in spaced relation to one another, with such mixing elements serving to mix the ingredients introduced into the trough. Further, a plurality of conveying elements and/or combination mixing-conveying elements are also disposed along the shaft 36. Numerous forms and arrangements of such elements can be utilized in the present invention, provided that they perform the necessary function for operation of the mixing trough. Thus, it should be appreciated that the illustrated form and arrangement of such mixing elements is not necessarily the sole arrangement which will prove operative, but that the inventive concepts are concerned with the actual construction and the material of construction of the elements.

However, by way of exemplification, there is illustrated in FIGURE 4 a pair of composite helical screw flight section assemblies 40 affixed to the shaft 36 at the end corresponding to the inlet end of the chute 12. Since these composite flight section assemblies are disposed directly beneath the ingredients inlet area (FIGURE 2) they receive and initiate mixing of the separate ingredients entering the trough 10. A composite blade assembly 42 extends between the composite flight section assemblies 40 and creates an interference in flow by agitating the ingredients out of their normal flow path, which, as caused by the composite flight assemblies 40, is axial of the trough 10.

Adjacent the composite flight section assemblies 40, a plurality of composite mixing paddle assemblies 44 extend radially from the shaft 36. Although each paddle assembly 44 is generally perpendicular to the central axis of the shaft 36, the flat face of the paddle is disposed angularly to the plane of the end walls 20 and 22, much in the manner of an impeller blade. The paddle assemblies 44 are individually spaced axially along the shaft 36 and are further circumferentially disposed at spaced angles to one another. Thus, in a preferred configuration the second paddle assembly 44 is advanced some distance along the shaft 36 from the first paddle assembly 44 and is angularly spaced approximately about the periphery of circumference of the shaft. The third mixing paddle assembly 44 is axially advanced further along the shaft 36 and is angularly spaced approximately 120 from the second paddle assembly 44 and 240 from the first paddle assembly 44. The fourth mixing paddle assembly 44 is axially advanced still further along the shaft 36 and is angularly spaced about the shaft periphery to be in general alignment with the first paddle assembly 44. Additional paddle assemblies 44 are disposed in a similar arrangement following the same general configuration. A composite arcuate blade section assembly 46 extends across some of the mixing paddle assemblies 44 to scrape the trough walls and, at the same time, provide a lifting and dropping action for materials within the trough. Further along the shaft 36 there is a helical screw means in the form of a plurality of composite spiral flight assemblies 48 extending axially along and helically around the shaft 36, with such flight assemblies serving to form a sort of feeding screw which conveys material in the trough 10 toward the outlet opening 34.

Means 16 for operating the mixing and conveying means 14.is.in the form of an operating motor which serves to rotate the shaft 36 about its central axis. As illustrated, the means 16 is a hydraulic or pneumatic operating motor 50 connected to the end of the shaft 36 which projects forwardly beyond the front end wall 20. Such a motor 50 is provided with an inlet conduit 52 and an outlet conduit 54 which enables a fluid flow through the motor 50 to thereby cause the shaft 36 to rotate about its central axis. It will, of course, be understood that the means 16 is not limited to a pneumatic or hydraulic motor 50, but can equally well include an electric motor, a mechanical motor or the like.

In operation, the mixing and conveying means of a mixing trough used for combining ingredients such as one used to form concrete is subjected to an extreme amount of abrasive action by the materials being mixed. In order to minimize any wear and permit easy replacement of such worn parts the mixing and conveying means 14 of the mixing trough shown in FIGURES 1-3 is preferably constructed as shown in further detail in FIGURES 4-8. Removable wear plates 56, 58, 60 and 62 are removably affixed to flight sections 64, blade 66, mixing paddles 68, and spiral flights 70 in such combinations as will provide the necessary wear resistance. Thus, composite flight section assemblies 40 are made up of a pair of helical screw flight sections 64 with wear plates 56 fixed thereto in such a manner that the wear plates 56 relieve helical flight sections 64 of abrasive action. Similarly, wear plate 58 is fixed to blade 66, thereby making up composite blade assembly 42. In a like manner, wear blade 60 is fixed to paddles 68 to form composite mixing paddle assemblies 44 and a plurality of wear blades 56 are segmentally fixed to the spiral flights 60 thereby making up the composite spiral flight assemblies 48 which form a helical screw means. At each end of such resulting helical screw means is affixed a wear plate 62 rather than wear plate 56. The variouswear plates 56, 58, 60 and 62 are preferably fixed to their respective base members 64, 66, 68 and 70 by conventional mounting means such as nuts and bolts. Further, at least one flat Washer should be used between those wear plates attached to curved surfaces in order to provide a firm surface at the bolt area. Obviously, the actual size and shape of the various wear plates is dictated by the mixing and conveying elements themselves. 7 The outer edge of each wear plate is preferably flush with the outer edge of the respective base members 64, 66, 68 and 70, but this is not critical since if the wear plates extend beyond the base members they will eventually wear down to the base level and vice versa. While the wear plates are illustrated as aflixed to one side of each member, it should be understood that they can be attached to either the leading face, the trailing face, or both in actual use. The clear advantage of the novel construction is immediately apparent. If any one or several wear plates should Wear to the point where replacement is necessary, such worn plates can be removed and replaced by the worker in the field using simple tools and necessitating a minimum of down time. Instead of replacing a complete mixing and conveying assembly 14 in the shop, taking care that the new unit is properly installed in the bearings 38, the worker simply replaces the worn plate with another similar piece which does not have to be made to close tolerance.

Since the wear plates 56, 58, 60 and 62 will be subjected to extremes of abrasive action they should be constructed of a material which is capable of withstanding the abuse to which they will be put. Hardened steel could be used but even this material has been found to have the minimum acceptable wear and cost characteristics. Actually a material of abrasion resistance characteristics as good as hardened steel, which is defined herein as SAE 1020 annealed steel, can be used. It has been found that a nickel-containing, martensitic alloy of cast iron possesses excellent abrasion. resistance and is, therefore, the preferred material of construction of the wear plates. Such an alloy is that sold as Ni-Hard by the International Nickel Company, Inc., New York, N.Y. The Ni-Hard cast irons have been found to possess a microstructure similar to that of a heat-treated steel, but with a relatively larger proportion of carbide which contributes greatly to its abrasion resistance. The Ni-Hard irons can be either chill cast or sand cast, but it has been found that the chill cast alloy has a finer carbide size and, therefore, better abrasion resistance. In Table I can be seen a comparison of different ferritic materials in resisting the abrasive effects of wet silicate sand.

TABLE I.TYPICAL WET SAND ABRASION FACTORS l The abrasion factor is the ratio of weight lost by specimen during test to the weight lost by a standard specimen. This arbitrarily selected standard was annealed SAE 1020 steel 105-110 Brinell.

Ni-Hard castings come in four types, the choice of which depends on the use to which it will be put. Type 1 is a nickel-chromium white cast iron of good abrasion resistance. Type 2 has less carbon modification than type 1 and, therefore, is stronger and tougher but slightly less abrasion resistant. Type 3 has a high strength modification giving maximum toughness and good abrasion resistance. Type 4, with its higher alloy content, has superior corrosion and abrasion resistant properties. The abrasion factor of type 4 ranges from approximately 0.30 to approximately 0.40 according to the test described in Table I. Table II shows the chemical composition of the four Ni- Hard cast irons.

TABLE IL-OHEMIGAL PlgtggggTIES OF NI-HARD CAST Composition, percent Type 1 Type 2 Type 3 Type 4 Total carbon 3. 00-3. 60 2.40 (max) 1. 00-1. 60 2. -3. 60 Graphitie carbon, max. 0. 10 0. 10 0. 10 Silicon- 0 0. 40-0. 70 0. 40-0. 70 1. 50-2. 00

Phosphorous, max 0: 40

TABLE IIL-NOMINAL PROPE RTIES OF N I-HARD ALLOYS Type 1 Type 2 Type 3 Type 4 Sand Chill Sand Chill Sand Chill Sand Chill cast cast cast cast cast cast cast cast Brinell hardness, minimum (2 x 6 x 6 test blocks using tungsten carbide Brinell ball) 550 600 525 575 350-500 300-600 550 550 Tensile Strength, p.s.i. (1.20" diam. test bars) 40,000- 50, 000- 45, 000- 60, 000- 75, 000- 90, 000- 75, 000- 80,000-

' 50, 000 60, 000 55, 000 75, 000 125, 000 140, 000 85, 000 110, 000 Transverse strength, lbs. (1.20 diam. test bars, 12 span) 4, 000- 4,500- 4, 500- 5, 500- 6, 000- 8, 000- 5,000- 5, 500- 5,000 6, 800 5, 500 7,000 6, 400 10, 000 6, 000 7, 000 Transverse deflection, in. (1.?" diam. test bars, 12" span) 0. 08- 0. 08- 0. 10- 0.10- 0.08- 0.10-

0. l1 0. 12 0. 12 0. 12 0. 11 0... Izod AB Impact, ft., lb. (1.20" diam. unnotched bar struck 3 above support) -30 -40 25-35 35-55 60-70 70-100 35-15 35-45 Pattern shrinkage, in./tt z-A z-}4 0 25-0 Modulus of ElasticityXlO p.s.i. 24-26 Specific gravity 7. 6-7. 8 Density, lbs/in. 0. 275-0. 280 Coeflicient of Thermal ExpansionXlO- in 50200 F 4.5-5.0 4.5-5.0 50-500 F 6 3-6. 6 6. 3-6. 6 ISO-800 F 6 8-7. 1 6. 8-7. 1 Electrical resistivity, mlorohmcentimeters, 78 F 80 80-100 80 Thermal conductivity:

Cal. emr sea- C.-120 F 03 Cal: cm.- sec- G.450 F Magnetic properties Rockwell C har 76 F 1 Minimum.

While Ni-Hard type 4 cast iron is the preferred matethe ingredients to the outlet opening 34 the ingredients rial for the wear plates 56, 58, 60 and 62, it should be have been converted from separate dry and liquid inclearly understood that this invention is not limited there- 30 gredients to a relatively homogeneous, somewhat fluent,

to. Type 4 Ni-Hard is characterized by discontinuous carviscous composition of concrete. bide with a martensite or martensite-containing austenite As an adjunct to the positive action of the composite continuous phase. The type of carbide present in Ni-Hard mixing paddle assemblies and composite blade assemblies, type 4, however, is dependent on the chromium and silicon and the feeding screw, an additional mixing and combincontents. Referring to FIGURE 9 it can be seen that the 35 ing action is provided by the elastomeric wall 28 which chromium and silicon must be balanced inversely to procan freely bulge downwardly and outwardly, to thus creduce discontinuous carbide. ate a form of kneading action on the materials within As carbon content increases from 2.80 to 3.60 percent, the trough. It will be seen that the disposition of the shaft the amount of carbide in the structure increases and 36 within the trough 10 is such that the mixing paddle abrasion resistance consequently increases. However, tenassemblies and blade assemblies and the helical screw are sile strength decreases at a given percent of martensite in 1n substantial contact with the elastomeric bottom wall the matrix. 28, and thus the material being mixed is often forced be- Clearly, the mixing and conveying means of this inventween these elements and the bottom wall itself. As shown tion is adaptable for use in various forms of mixing apin FIGURE 3, the elastomeric bottom wall 28 contiguousparatus even though the preferred embodiment thereof ly contacts the mixing and conveying means 14, at least has been discussed in relation to a mixing trough means below the level of the shaft 36. Thus, the combination and of the type described. Turning now, therefore, to the coaction between the mixing and conveying means 14 manner of operation of the mixing trough 10 and the and the elastomeric bottom wall 28 creates a powerful novel mixing and conveying means 14, it will be noted positive agitating, mixing and conveying action which by referring to FIGURE 2 that a plurality of inlet contransforms the various separate ingredients into a homoduits are provided in juxtaposition above the rearward end geneously combined composition. Accordingly, when any of the chute 12. Since the mixing trough 10 is particularly Wear plate wears to the point where there is not substanadapted for use in forming concrete, the illustrated inlet tial contact between the same and the elastomeric bottom conduits are labelled gravel, sand, cement and water. It Wall 28 it should be replaced, For example, in a composite is again emphasized that the invention is not limited to a flight section assembly which measures approximately 3% trough which will mix these particular ingredients, but inches from the shaft 36 to the outer edge of the wear rather to one that will accommodate any form of ingrediplate 56, if any of the wear plates 56 should wear down t to between about 3 inches and 3% inches, it should be When the ingredients are introduced into the inlet end replaced. of the chute 12 they are initially mixed by the composite 60 In a preferred aspect of this invention in a mixing flight section assemblies 40 and are scraped off the chute trough the mixing trough 10 is disposed at an angular walls and bottom by the composite blade assembly 42. relationship during the mixing operation so that the mix- These initially mixed ingredients then feed past the coming and conveying always takes place against the action posite mixing paddle assemblies 44 which tend to spin of gravity. This can be understood by reference to FIG- the ingredients about the inside of the chute, while at URE 2 wherein the chute is shown disposed at an acute the same time agitating and forcing the ingredients toward angle a above a horizontal axis H. The exact manner in the outlet end of the trough. The composite arcuate blade which the chute is pivoted or pivotally mounted to enable assembly 46 scrapes the ingredients off the trough walls it to assume this position is not necessarily critical, and and bottom, and at the same time tends to lift and drop any suitable pivot mounting means at the inlet end of the mixture into the interior of the trough, thus creating the chute will be sufficient. For purposes of simplicity of a form of tumbling action which aids in mixing. Next, illustration, outwardly extending pivot shafts 76 project the composite spiral flight assemblies 48 of the screw refrom the rear portion of the sidewalls 18, and it is underceive the mixture, and as they rotate, they feed the mixed stood that these pivot shafts can be journaled in any suitingredients forwardly, while at the same time still further able bearing means. Thus, the chute is pivotally mounted mixing the same. When at last the feeding screw delivers about its inlet end. To enable the trough 10 to be maintained in its upward angular disposition, an eye 78 is attached to the upper portion of the forward end wall 20, and a hook or clamp 80 may be engaged with this eye as shown in FIGURE 1. A cable 82 can extend from the clamp 80 to a winch or other suitable means which when operated, causes the trough to pivot upwardly about its pivot point. The precise value of the angle at is not particularly critical, provided only that such angle be an acute angle. An angle between 15 and 22 has proved useful in practice.

The sidewalls 18 are sloped generally inwardly from their upper to their lower edge as can be seen in FIG- URE 3. Thus, the material is generally directed inwardly and downwardly toward the bottom of the trough. Since the trough is disposed at an acute angle a above the horizontal, the force of gravity has a component acting downwardly against the bottom wall 28 and further has a component directed toward the end wall 22 at the inlet of the trough. Thus, when the mixing and conveying action takes place, it must act against the force of gravity. In other words, not only must the mixing paddle assemblies lift the material from the bottom wall of the chute upwardly and back downwardly again, but moreover, the mixing, as well as the conveying, must direct the material in an axial direction toward the outlet opening 34, against the force of gravity.

As a safety measure to prevent an operator from inadvertently moving his hand into contact with the mixing and conveying means 14, and additionally, to prevent any large pieces of debris from falling into the chute, a grillwork may be provided above the mixing and conveying means 14. Such grill-work can take the form of a pair of elements 84 extending transversely of the chute, and a series of rods 86 extending longitudinally of the chute and being mounted upon the elements 84.

It will be apparent from the foregoing detailed description that the objects set forth at the outset of the specification have been successfully achieved through utilization of the present invention.

Accordingly, what is claimed is:

1. In an elongated mixing trough having an elastomeric bottom portion, a shaft means mounted longitudinally therein, means for rotating said shaft means, and a spirally shaped conveyor mounted on said shaft means to mix and convey material in said trough, the improvement comprising:

(a) a plurality of wear plates, each comprising a fraction of one convolution of said spirally shaped conveyor,

(b) said wear plates being secured on said conveyor in end to end relation to compositely define a wear resistant spiral edge on said conveyor,

(c) said edge cooperating with said elastomeric bottom portion to mix said material while the same is conveyed along said trough,

(d) said wear plates being made of a composition at least as abrasion resistant as hardened steel.

2. The improvement defined in claim 1 wherein said composition has a wet sand abrasion factor of about 0.25 to about 0.60.

3. The improvement defined in claim 2, wherein said composition has a wet sand abrasion factor of about 0.30 to about 0.40.

4. The improvement defined in claim 1, wherein said wear plates are fabricated of a cast iron alloy of the following composition:

Percent. (a) total carbon 1.00-3.60 (b) graphitic carbon, max. 0.10 (c) silicon 0.40-2.00 (d) manganese 0.40-0.70 (e) nickel 4.00-6.50 (f) chromium l.40-10.00 (g) sulfur, max. 0.10-0.5 (h) phosphorous, max. 0.25-0.40

the remainder being essentially iron.

5. The improvement defined in claim 1, wherein said alloy is composed of:

Percent (a) total carbon 2.80-3.60 (b) graphitic carbon, max 0.10 (c) silicon 1.50-2.00 (d) manganese 0.40-0.70 (e) nickel 5.50-6.50 (f) chromium 7.0-10 (g) sulfur, max. 0.10 (h) phosphorous, max 0.25

the remainder being essentially iron.

References Cited UNITED STATES PATENTS 1,555,964 10/1925 Guedel 259-178 3,339,898 9/1967 Futty 259--148 ROBERT W. JENKINS, Primary Examiner 

